Roof supports



Feb. 3, 1959 A. w. DUNCAN 2,872,147

ROOF SUPPORTSl Filed Aug. 26, 1953 ROOF SUPPORTS Angus Wellesley Duncan, Worcester, England, assignor to The Mining Engineering `Company Limited, Worcester, England Application August 26, 1953, Serial No. 376,630

Claims priority, application Great Britain September 5, 1952 6 Claims. (Cl. 248-351) This invention relates to mine roof supports and more particularly to hydraulic units for incorporation in such supports.

Roof supports used in mines are commonly props extending between roof and oor or chocks comprising members laid across each other in hollow square forma tion or a combination of such members with a built up base. It is common practice to tighten such roof supports in position by driving in slow taper wedges and thus the support initially takes a proportion of its nal load but such proportion is relatively small.

The object of this invention is to provide means for preloading chocks or props to a relatively high proportion of their nal load capacity which can be used in conjunction with known types of chocks or props and which is independent of outside sources of power other then the manual effort required to operate a control valve.

Briefly, the invention comprises a roof support unit for incorporation in a chock structure or with a roof prop comprises a hydraulic cylinder, a separate compartment within the unit comprising a hydraulic accumulator in communication with the cylinder, a ram working within the cylinder and arranged to bear directly on the cylinder at one end of its stroke and a manually operated valve operable to connect the cylinder directly to the hydraulic accumulator or to isolate the accumulator. Specifically, the preferred embodiment of the unit for incorporation in a chock structure comprises chock pieces arranged in hollow square formation, a unit having four cylinders arranged at the corners of a square, each cylinder having a ram slidable therein with a head' on which chock pieces may be laid, an hydraulic accumulator within the unit, uid channel means connecting each cylinder to a cornmon fluid passage to the accumulator cylinder and a manually operable valve controlling this common passage, whereby said accumulator rnay at will be isolated from or connected to all of said cylinders. A second passage from the accumulator to all of the cylinders may be provided with a spring biased nonreturn valve whereby on the fluid pressure within the cylinders increasing beyond a value determined by the spring the valve opens and permits uid to ilow from the cylinders into the accumulator.

Other parts of the invention are embodied in the preferred form which will now be described in some detail by way of example with reference to the accompanying diagrammatic drawings in which Fig. l is a side view of a chock structure incorporating one embodiment of the invention, parts being broken away for clarity and Fig. 2 is a sectionv on the line II-II of Fig. 1.

As shown in Fig. 1 a chock structure built up between the roof and oor of a mine comprises timber chock pieces 1, and conventional chock releases 2 built up in hollow square form on a base unit 3. The structure is tightened between roof and oor by timber wedges 4 in the usual manner.

The base unit 3 comprises a metal structure 5 which icc.

suitable manner and which is therefore only indicatedl diagrammatically in the drawing.

The base unit 3 is substantially square in plan and supports at each corner, an hydraulic cylinder 6. In each cylinder slides a ram 7 having an enlarged head plate 8. The arrangement is such that this head plate contacts the top of the cylinder 6 when the ram is in its lowest position.

Supported in the base unit 3 is an hydraulic accumulator comprising a cylinder 9 in which slides a piston 10. In the form shown, the cylinder 9 is arranged with its axis horizontal but may of course have its axis vertical if desired.

The piston 10 has a deep recess 11 on one side and the cylinder on this side of the piston contains compressed air which can ibe loaded into the cylinder through a plug 12. The cylinder on the other side of the piston contains hydraulic iuid. This end of the cylinder 9 is connected by two uid conduits 13 and 14 to a system 15 of iluid conduits which lead to the hydraulic cylinders 6.

One iluid conduit 13 is controlled by a manually operable valve 16 whereby the accumulator cylinder 9 can be connected to the cylinders 6 or may be isolated therefrom. The other fluid conduit 14 contains a non-return valve 17 biassed by a spring to close the conduit against ow of fluid from the accumulator cylinder 9 to the conduit system 15 whilst permitting fluid to flow in the opposite direction.

it will be apreciated that the accumulator capacity is such that it can accommodate the whole of the pressure fluid displaced by the stroke of the rams 7 The stroke of the ram is of the order of 1" or 2".

The chock is built up on the headplates of the rams 7. As shown, two chock releases are laid on the head plates each release extending across two rams and lying parallel to the side of the unit but timber chock pieces may be placed on the ram in a similar manner.

The chock structure is built up and tightened in the usual manner .by the wedges 4. As the roof and floor of the mine converge, the accumulator 9 being in co-mmunication with the main cylinders 6 the rams 7 move into the cylinders until the head 8 engages the cylinder and the pressure, fluid displaced has passed through the valve 17 and/ or 16 into the accumulator. Thereafter the resistance offered to the roof by the chock is the crushing load of the component parts or of the mine strata.

The pressure built up in the accumulator is available when the unit is incorporated in a roof support in a different position in the mine to preload the support to a high proportion of its full load capacity. When it is desired to move the chock the valve 16 is operated to isolate the accumulators, the chock collapsed in the usual way and rebuilt in its new location. The valve 16 is then operated to connect the accumulators to the cylinders and the rams move out to preload the chock.

It will be appreciated that a similar device of suitable size (probably utilizing only one cylinder and ram) can be used in conjunction with a prop of known type to preload it to a high proportion of its full load capacity.

Some idea of the preloading achieved will be apparent from a consideration of a particular case in which four rams each of 6 in. eifective diameter are built into a chock. Supposing the accumulators have a working range of 2,500 to 3000 lbs. per sq. in. the load at which the rams close will be 37.8 tons per ram or 151.2 tons on the chock. The load with the rams extended (that is the minimum preload exerted on the chock) will be 31.5 tons per ram or 126 tons on the chock. In practice, chocks normally carry maximum loads of to 160 tons.

It Will be understood that the invention is not re- Patented Feb. 3, 1959.

stricted to the details of the preferred form described which vmaryr*be-irnodiiiedwithout'depa'rting from the broad ideas underlying them` I claim:

1. A mine roof support conjlprisingvin` combination, chock pieces,-collapsible chlocl; releases and aunit comprising a hydraulic cylinder, a ram' working within said cylinder said ram beingretracted into said cylinder by subsidence of the supported roof, and bearingon said cylinder when fully retracted therein, an hydraulic cumulator in communication with' said cylinder and charged with fluid by the retractions of said ram within said cylinder, and a manually controlled' valve operable to isolate said accumulator from: said cylinder.

2. A mine roof support comprising in combination, chock pieces, collapsible chock releases and a base unit comprising n plurality of rams adapted to support chock. pieces, a plurality of cylinders in each of which a ram is slidable, said rams being retracted into said cylinders by mine roof subsidence, an hydraulic accumulator, a iluid conduit system connecting said" accumulator to cach of said cylinders, retraction of said rams Within said cylinders charging said accumulator by forcing uid from said cylinders through said conduit system, and valve means controlling said uid conduit system and manually operable to isolate all of said cylinders simultaneously from said accumulator.

3. A mine roof support comprising in combination, chockl pieces, collapsible chock releases and a base unit comprising a pluralityl of rams adapted to support chock pieces, a plurality of cylinders in each of which one of said rams is slidable, said rams being retracted into said cylinders by mine roof subsidence, an hydraulic accumulator, a uid conduit system connecting said accumulator to each of said cylinders, retraction of said rams within said cylinders charging said accumulator by forcing uid from said cylinders through said conduit system, valve means controlling said uid system and manually operable to isolate all of said cylinders simultaneously from said accumulator, Aand nonreturn valve means insaid-huid conduit system to permit uid to pass from said cylinders to said accumulator and to prevent passage of fluid in the reverse direction.

4. A mine roof support comprising in combination, chock pieces, collapsible chock releases, and a ibase, a plurality of cylinders in the upper part of said base,

rams slidable in said cylinders and adapted to support said chock pieces and chock releases, said rams being retracted into said cylinders by mine roof subsidence, a hydraulic accumulator in said base, a iuid conduit system connecting said Vaccumulator to each of said cylinders, retraction of the rams Within the cylinders forcing iluid from the cylinders through the conduit system into the accumulator, and valve means controlling said fluid conduit system.

5. A mine roof support according to claim 4 wherein said valve means comprises a manually operable valve controlling a connection between'said accumulator and all of said cylinders and a nonreturn valve permitting liuid to pass from said cylinders into said accumulator and preventing the passage of iiuid in the reverse direction.

6. A mine roof support according to claim 4 wherein each ram has an enlarged head adapted to engage the cylinder in which the ram slides when the ram is fully retracted into the cylinder.

References Cited in the le of this patent UNITED STATES PATENTS 1,964,003 McBride June 26, 1934l 2,657,028. Joy Oct. 27, 1953 FOREIGN PATENTS 493,811 Belgium Feb, 2s, 1950y 507,045 Great Britain June 8, 1939 623,945 Germany Jan. 8, 1936 828,836 Germany Jan. 21, 1952 1,016,105 France Aug. 20, 1952 

